The present invention is directed to underwater acoustic sensor systems, and more particulary to acoustic baffles for underwater acoustic sensors.
In the design of underwater acoustic systems, it is sometimes necessary to use a reflecting baffle to direct the acoustic signal. The requirements for a good reflector are that the acoustic impedance of the reflector be very much larger or very much smaller than that of water. Reflectors having a much greater impedance than water are very massive and therefore not practical for many applications, such as when the transducer system must be suspended from buoys. Sometimes resonant-type baffles may be used, such as compliant tubes which are made of metal and are hollow with air inside. These baffles are very much less massive than solid baffles of high-density material, but they are only useable over a limited frequency band around which resonance occurs. Very low density materials which have very low acoustic impedance have also been used. These materials, such as cork-rubber compounds or closed cell foam rubber, cannot sustain the hydrostatic pressure of great ocean depth, as they become compressed under pressure and begin to approach the acoustic impedance of water.